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| United States Patent |
6,210,799
|
|
Berger
, et al.
|
April 3, 2001
|
Industrial yarn PA 6.6 with little cotton waste
Abstract
Industrial yarn PA 6.6 comprised of filaments having a global yarn count of
at least 900-2100 tex, which is made by submitting wet granulate PA 6.6 to
a melt spinning-drawing process, is characterized by a strength of >84
cN/tex for less than 1.5 linters/1 km. Said yarn is used preferably in the
production of cord fabric with a rubber ply.
| Inventors:
|
Berger; Luzius (Malters, CH);
Fischer; Klaus (Luzern, CH);
Luvizotto; Jose (Sao Cactano do Sul, BR)
|
| Assignee:
|
Rhodia Filtec AG (Emmenbruecke, CH)
|
| Appl. No.:
|
509092 |
| Filed:
|
May 15, 2000 |
| PCT Filed:
|
September 22, 1997
|
| PCT NO:
|
PCT/CH97/00357
|
| 371 Date:
|
May 15, 2000
|
| 102(e) Date:
|
May 15, 2000
|
| PCT PUB.NO.:
|
WO99/15721 |
| PCT PUB. Date:
|
April 1, 1999 |
| Current U.S. Class: |
428/364; 428/395 |
| Intern'l Class: |
D01F 006/00; D01F 006/90 |
| Field of Search: |
428/364,395
57/288
528/335
|
References Cited
U.S. Patent Documents
| 4648240 | Mar., 1987 | Hallsworth et al. | 57/288.
|
| 5106946 | Apr., 1992 | Clark, III et al. | 528/335.
|
| 6023824 | Feb., 2000 | Fishcher et al. | 28/240.
|
Primary Examiner: Edwards; N.
Attorney, Agent or Firm: Striker; Michael J.
Claims
What is claimed is:
1. A PA 6,6 industrial yarn consisting of filaments having a total linear
density of 900 to 2100 dtex and produced by melt-spinning and drawing of
polyamide-6,6 having a pellet viscosity RV >75 at a winding speed v.sub.sp
which has to meet the following conditions:
v.sub.sp =(Ft.sub.o /Ft.sub.x).sup.3 *v.sub.spo, where Ft=tenacity,
Ft.sub.o =84 cN/tex, Ft.sub.x =eff Ft in cN/tex and v.sub.spo =2750 m/min
(1)
in the presence of water, characterized in that the PA 66 filament yarn
combines a tenacity of >84 cN/tex and with less than 1.5 defects/km.
2. A PA 6,6 industrial yarn according to claim 1, characterized in that the
number of defects at a pellet viscosity RV >90, a moisture content >0.06%
and a tenacity Ft >90 cN/tex conforms to the following formula:
defects F1<(Ft.sub.x /Ft.sub.o).sup.3 *v.sub.spx /v.sub.spo *Tt.sub.x
/Tt.sub.o,
where (2) Tt.sub.o is a linear density of 940 dtx and Tt.sub.x is the
linear density at the winding speed v.sub.spx.
3. A process for producing PA 6,6 industrial yarn according to claim 1
having a total linear density of 900 to 2100 dtex by melt-spinning
polyamide-6,6 having a relative pellet viscosity (RV) of at least 75 in
the presence of water, characterized in that the water content of the PA
6,6 polymer after addition of the water ahead of the extruder is
0.04-0.14% by weight.
Description
The present invention relates to a PA 6,6 industrial yarn consisting of
filaments having a total linear density of 900 to 2100 dtex and produced
by melt-spinning and drawing of polyamide-6,6 having a pellet viscosity RV
>75 at a winding speed v.sub.sp which has to meet the following
conditions:
v.sub.sp =(Ft.sub.o /Ft.sub.x).sup.3 *v.sub.spo, where Ft=tenacity,
Ft.sub.o =84 cN/tex, Ft.sub.x =eff Ft in cN/tex and v.sub.spo =2750 m/min
(1)
in the presence of water, and also to a process for producing a low-defect
industrial yarn.
As well as its serimetry, its level of defects is a significant quality
factor of an industrial yarn. At winding speeds of more than 2750 m/min,
polyamide industrial yarns generally have an excessively high defect level
of the order of more than 1.5 defects per km. To reduce defects, it was
hitherto necessary to reduce the spinning speed, which entails reduced
productivity. It has now been found that the defect level depends not only
on the spinning and winding speed but also, strongly, on the moisture
content of the polyamide polymer fed into the extruder.
It is known to moisten PA 66 polymer ahead of the extruder or in the melt.
In each case the purpose is to ensure consistent melt quality. The
moisture is added in controlled fashion via moist N.sub.2 or as direct
metered addition of water, for which the melt pressure ahead of the
spinning pump can be utilized as control variable.
EP-B-0 092 898 discloses controlling physical properties of meltable
polyamides by depolymerization by means of moisture. In said reference,
water is added to keep the viscosity constant. The object is considered to
be to produce a polymer melt having constant physical properties.
The present invention has as its object to provide a PA 66 industrial yarns
having a tenacity of at least 84 cN/tex, very rapid processing and a
minimum of defects.
This object is achieved according to the invention when the PA 6,6 filament
combines a tenacity of >84 cN/tex and with less than 1.5 defects/km.
In a variant featuring a pellet viscosity RV >90, a moisture content >0.06%
and a tenacity Ft.sub.x >90 cN/tex, it is possible to obtain at a spinning
speed v.sub.spo greater than the spinning speed calculated by the formula
(1) an industrial yarn having a high linear density and a surprisingly low
number of defects conforming to the following formula:
defects F1<(Ft.sub.x /Ft.sub.o).sup.3 * v.sub.spx /v.sub.spo *Tt.sub.x
/Tt.sub.o, where (2)
Tt.sub.o is a linear density of 940 [lacuna] and Tt.sub.x is the linear
density at the winding speed v.sub.spx.
The advantage is a low defect level which, if dry PA 66 polymer pellets are
used, can otherwise only be achieved at low spinning-drawing speeds.
It is particularly advantageous for the water content of the polymer
pellets ahead of the extruder to be in the range of 0.04-0.14% by weight,
especially 0.06-0.12% by weight.
The invention will now be more particularly described with reference to an
example.
A polyamide-6,6 polymer post-condensed to a relative viscosity (RV) of
about 93 was admixed ahead of the extruder with varying quantities of
water so that the resulting total moisture content of the polymer varies
between 0.16 and 0.02%. The winding speed was 2750 m/min in all runs. The
throughput was a constant 46 kg/h. The tenacity Ft was likewise constant
at 85 cN/tex.
The relative pellet viscosity was measured in 90% strength formic acid
using ASTM method D 789-81.
Defects were measured using a Warpstop 450 from Protechna, FRG. Each test
was carried out with 24 packages.
The results are depicted in FIG. 1. FIG. 1 shows the plot of the number of
defects against the water content of the PA 6,6 polymer pellets ahead of
melting. Curve 1 demonstrates the dependence for a linear density of 940
dtex with a pellet RV of 93 and a throughput of 46 kg/h; curve 2
demonstrates the defect trajectory under otherwise identical conditions
for a linear density of 1400 dtex, whose curve trajectory is broadly
similar.
As is further evident from FIG. 1, the defect level initially decreases
dramatically with increasing water content in the feed polymer. At a water
content of 0.02%, the moisture content ex dryer, a winding speed of 2750
m/min produces defect numbers of around 5 defects per kilometer. At a
water content of about 0.09%, surprisingly, minimum values are achieved in
relation to defects. As the water content continues to increase, defects
increase again sharply.
Further examples are recited in the following Table I.
TABLE I
Linear Winding
density speed Vsp Tenacity Ft Number of H.sub.2 O
No. [dtex] [m/min] [cN/tex] defects/km [%]
1 1880 2260 92.6 1.7 0.08
2 1400 2040 94.2 1.6 0.08
3 2100 2050 92.7 2.0 0.08
4 1400 2750 84 3.5* 0.02
5 1400 2750 84 0.7 0.07
*without addition of water
The yarns recited in Examples 1-3 are known as super high tenacity (SHT)
yarns, whereas the yarns recited in Examples 4 and 5 are known as HT
yarns. In each case, a polymer having a relative pellet viscosity RV 93
was spun.
It is evident that less than 1.5 defects per km are achieved at a water
content of 0.04 to 0.14 and less than 1 defect per km is achieved at a
water content of 0.08 to 0.11. The polyamide yarn of the invention has
half the defect level of the prior art. The yarn is preferably suitable
for producing cord fabrics for use in rubber, for example for transport
belts, drive belts and automobile tyres.
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